Three key points need to be made in order to answer your question thoroughly:

1- What is the Unseen?

Gheyb or unseen, means for something to be concealed from the senses. It is defined as: الغیب: کل ما غاب عنک; meaning that anything that is hidden from you is considered gheyb and unseen.[1] This is why when the sun sets, Arabs say: “غابت الشمس”; meaning that the sun became hidden and unseen.[2]

When this term is used as the opposite of shahadah or “the seen”, which is a Quranic and theological term, it refers to something metaphysical and outside this natural world that can't be sensed with the normal senses and if one ever wants to actually sense it, he will need to use other methods.

Allamah Tabatabai says: Gheyb and Shahadah are two proportional concepts, meaning that something might be gheyb in relation with one thing, while being shahadah in relation with another; the reason being that all things in this world have their boundaries they cannot be separated from. Therefore, anything that comes inside their boundaries will be subject to their comprehension, thus making them shahadah, because they are something that is comprehended by them. On the other hand, anything that doesn’t enter their boundaries will be gheyb, because it is something that isn't subject to their comprehension.”[3]

2- Who is aware of the gheyb (unseen) and possesses its knowledge?

What the explanation of gheyb given above entails, is that knowledge of the gheyb and being aware of the unseen, is something that only Allah (swt) completely possesses, because He is the only one who has total dominion and awareness of the entire universe and everything it encompasses; nothing lays outside His existential boundaries, and nothing can conceal itself from Him. This subject has been pointed to in different ways by the Holy Quran:

“Allah is the Knower of the Unseen and The Visible; and He is the Supreme Exalted Great”[4]

“They say:" Why was not a Miracle Sent down upon him from his Creator and Nurturer?" Say [O, Messenger!]:" The knowledge of the Unseen is only For Allah”[5]

“Say," No one in the heavens or the earth knows the Unseen except Allah”[6]

The first thing one understands from such verses is that no one other than Allah (swt) is completely aware of the unseen, nevertheless, there are verses that state that there are others of those who are apostles of Allah (swt) who also know some things regarding it:

“Allah will not acquaint you with the Unseen, but Allah chooses from His apostles whomever He wishes [to inform of the unseen]”[7]

“Knower of the Unseen, He does not disclose His Unseen to anyone, except to an apostle He approves of”[8]

When speaking of Prophet Isa’s (pbuh) miracles, the Quran says:

“And I will tell you what you have eaten and what you have stored in your houses”[9]

In addition to these verses, there are also many hadiths that show that the prophet (pbuh) and imams (as) have some knowledge of the unseen; this knowledge being in two forms:

The first form being when the prophet (pbuh) would inform of revelation being revealed; this itself is a form of the unseen which he had.

The second form: The precise prophecies they made, like when the prophet (pbuh) informed of the battle of Mutah (موته) and of the martyrdom of Jafar and other commanders of the Islamic army while he was in Medinah with the people, right when it all happened.[10] In many hadiths, the knowledge of the imams regarding the unseen has been emphasized.[11] One can claim that these hadiths even reach the degree of tawatur.[12]

As for how the hadiths and the second group of verses mentioned (that imply that others other than Allah (swt) are also aware of the unseen) aren't in contradiction with the first (that imply it is only Allah (swt) who has knowledge of the unseen), one can say the following:

1- Knowledge of the gheyb originally and primarily belongs to Allah (swt). He independently possesses it without anyone else having given it to Him, but others who might possess some of it, never independently obtain it, it is always bestowed upon them by Allah (swt), making them dependant on Him for it.

2- Allah (swt) is the only one to know every single detail of the unseen, while others only have a general overview.

3- Allah (swt) knows of all secrets of the unseen at the very moment and others aren't, yet only if Allah (swt) wills, they can be informed as well, or if they will, given that their will is backed by Allah's (swt). Imam Sadiq (as) has been reported saying: “Whenever the imam wishes to know something, Allah (swt) teaches him.”[13]

In addition to this, there are verses that speak of a specific type of knowledge that is obtained through self-building and practicing religion and spirituality and movement towards the truth. Verses like: “O you who have faith! If you are wary of Allah, He shall appoint a criterion for you [enabling you to distinguish between right and wrong], and absolve you of your misdeeds, and forgive you, for Allah is dispenser of a great grace”.[14]

Also, when Imam Ali (as) would recite the verse: “…by men whom neither trading nor bargaining distracts from the remembrance of Allah…”[15], he would say: “Certainly, Allah (swt), the Glorified, the Sublime, has made His remembrance the light for hearts which hear with its help despite deafness, see with its help despite blindness and become submissive with its help despite unruliness. In all the periods and times when there were no prophets, there have been persons with whom Alláh, precious are His bounties, whispered through their wits and spoke through their minds”.[16]

3- The third central point of this discussion:

Now we will engage in discussing a bit about verse 34 of surah Luqman:

“Indeed the knowledge of the Hour is with Allah. He sends down the rain, and He knows what is in the wombs. No soul knows what it will earn tomorrow, and no soul knows in what land it will die. Indeed Allah is all-knowing, all-aware”.[17]

There are two explanations for this verse:

1- This verse correlates with the verse preceding it which speaks of the hereafter; it speaks of things that are of the unseen belonging only to Allah (swt), which we call “knowledge of the unseen”. This verse points to five things that are all of the unseen:

a) Knowing when the hereafter will take place: This is something the mushriks have asked the prophet (pbuh) about many times: “When is the hereafter?”[18] The Quran answers them saying: “Indeed the Hour is bound to come: I will have it hidden, so that every soul may be rewarded for what it strives for”.[19]

b) When it will rain: The knowledge of when and where it will exactly rain and how much, are all in the possession of Allah (swt), and others can only guess about them.

c) What is in the womb of mothers: Meaning the gender and inner and outer characteristics of the fetus. Therefore, although there are ways of finding out its gender, yet there is no way to find out about its physical and spiritual traits, potentials and thousands of other characteristics that it has; all of this is only known of by Allah (swt).[20] Also, the future of the fetus and whether it will reach salvation or damnation in this world are all things that only Allah (swt) can know of.

d) Future incidents and their details and what each person will do in the future.

e) And finally, where every person will die.

According to this explanation and interpretation or tafsir, all of the above are considered part of the unseen, whose knowledge only belongs to Allah (swt). If one asks: “Then how come some of the above were known by the imams according to hadiths?”, the answer will be that knowing only a portion of them through Allah's (swt) teaching is in no contradiction with the exclusive allocation of their detailed knowledge to Allah (swt). At the same time, they (the infallibles) aren't independent in their knowledge, but are totally dependent on Allah's (swt) teaching, to the amount He sees fit.[21]

2- Some sections of this verse differ from others; their way of speaking and tone varies. The first phrase of this verse tells us that the knowledge of when the hereafter will take place only belongs to him and no one else is aware of it. According to Arabic literature rules, this exclusiveness can be concluded by the fact that the word “عنده” has been mentioned before “علم الساعة”. Other verses also stress that such knowledge only belongs to Allah (swt).

But in the second section of the verse, we see that the verses style of speech changes and there is no implication of exclusiveness. What can be concluded from this part is that Allah (swt) is aware of when it will rain and what is in the wombs of mothers, without anything being said about anyone else knowing or not.

Therefore, Allah's (swt) knowledge regarding when it will rain and the fetus in the womb of the mother, in no way means that certain servants of His also can't learn of them in other ways such as divine revelation and inspiration. The only difference between Allah's (swt) knowledge and their’s being that His originally belongs to Him, while others acquire and obtain it and it doesn’t essentially belong to them.

In the fourth and fifth parts of the verse, its tone changes even more. They mainly speak of the fact that Allah (swt) knows where each person will die. Not knowing where one will die is in conformity with nature’s laws that say no one essentially knows of the unseen and what is going on on the other side, nevertheless, this doesn’t mean that Allah (swt) can't inform any of His servants of their future and where they will die.[22]

To sum it all up, this second interpretation of the verse says that with help from other verses and the first part of this verse, one concludes that knowing of when the hereafter will take place is something that only Allah (swt) knows of and no one else.